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BELL RINGER. What are the three subatomic particles? (Things smaller than an atom, you learned in 8 th grade). History of the Atom. Where it all began…. history. The atom starts not with the ________ of the atom, but the ______ of the atom. idea.
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BELL RINGER What are the three subatomic particles? (Things smaller than an atom, you learned in 8th grade)
Where it all began… history The atom starts not with the ________ of the atom, but the ______ of the atom. idea More than ______ years ago, (around ____ BC) Greek philosophers, ___________ and ____________ debated the nature of the universe. 2000 400 Democritus Aristotle Aristotle Democritus
Get this… Aristotle believed that all matter was made of ___ elements: ______, ____, ______ and _______. 4 Earth Air Fire Water Democritus believed that matter was made of small particles called ______ that cannot be _____________. atoms broken down
Who WON the debate and who was RIGHT? Democritus based his theory on ___________, Aristotle based his on __________. Neither of them really did _____________. observation philosophy experiments _______ argued louder, so he won. Aristotle’s ideas then carried through until the _____________. Democritus was actually _______. Aristotle Middle Ages RIGHT
What happened next? A branch of science called _________ was introduced to Europe in ______ AD. alchemy 1144 Alchemists tried to change ______ to ______. lead gold “SHOW ME THE MONEY!”
Alchemy Symbols Alchemists were ___________ in changing lead to gold – a process called _____________ *(_________ one substance into _______.)* unsuccessful transmutation Changing another
The Father of Atomic Theory Modern atomic theory was developed in 1809 by an English scientist named _____ ________. John Dalton His theories were based on ___________ and ___________. observations experiments Dalton’s Atomic Theory Matter is made of small particles or atoms. Atoms cannot be created or destroyed. All atoms of an element are identical and have the same mass. Atoms of different elements have different masses. Compounds are formed by combining different elements.
Who’s Next? In _____, an English physicist named ______________ did experiments to determine the parts that make up the atom. 1897 J.J. Thomson He created a ________ ray tube: a _______ tube where all the ____ has been pumped out and a limited amount of other ______ is pumped in. cathode vacuum air gases
Voltage source Thomson’s Experiment - + Metal Disks
Voltage source Thomson’s Experiment - + • Passing an electric current makes a beam appear to move from the negative to the positive end
Voltage source Thomson’s Experiment + - • By adding an electric field to the outside of the tube, he discovered that the moving pieces were negative.
EUREKA! The negatively charged particles were called corpuscles by Thomson but the name was later changed to ________. electrons Thomson developed a model based on his findings and it was called the ____________ model. plum pudding Positive “pudding” Negative “plums”
Next up… In _____, an English physicist named _________________ continued Thomson’s work. 1910 Ernest Rutherford He believed the plum pudding model was correct, but wanted to discover the _____ of atoms. size
Rutherford’s experiment To do this… Rutherford used thin ________ sheets and ___________ material. gold foil radioactive alpha The radioactive material released ______ particles, which would _____ when in contact with the fluorescent screen. glow
This is what it looked like: Fluorescent Screen Uranium Lead block Gold Foil
He thought… The alpha particles would pass through the foil without ________ _________. changing direction Because… The _______ charges would be spread out _______, and were not close enough together to repel the positively-charged alpha particles. positive evenly
Why this? Positive alpha particles Positive “pudding”
+ Explanation please: Atoms are mostly ______ ______. empty space Nucleus There is a ______, _______, ________ charged area at the center of the atom – called the ________. small dense positively nucleus The positive alpha particles were _________ by the nucleus if they got close enough…and thus we have the _______. deflected proton
+ Like Charges REPEL!
The Bohr Model The next model of the atom comes from a Danish chemist, _____ _____, who developed it in _____. Niels Bohr 1913 In this model the ________ are located in the nucleus and the protons _________ are located in pathways around the nucleus. electrons
Modern Model of the Atom The wave mechanical or electron cloud model was introduced in ______ by Schrodinger and Heisenberg. 1926 In this model the electrons do NOT follow a set path, they have wiggle room. Because of this you cannot predict the location of an electron at a given time.
Last but not least… Chadwick James _________ discovered the last subatomic particle in _____. The _______ was so difficult to find because it does not have a ______, it is _______. Chadwick’s discovery earned him the nickname: ______________ (sound familiar?) 1932 neutron charge neutral Jimmy Neutron
BELL RINGER Name a scientist who helped with the history of an atom and tell what he explained about the atom.
Make a TIMELINE! • Using your notes, make a timeline of Atomic Events in History! • Use the paper provided and the colored pencils! • Make it creative, but ACCURATE! • Include pictures, too!
